Other than by corrupt criminals and mafia types who have a need to covertly hide cash.
And then the current administration wants the government to 'protect' crypto investors against big losses. Gotta love it.
And anyone who lives in a polity whose local currency may be undergoing rapid devaluation/inflation.
And anyone who needs a form of wealth that no local authority is technically capable of alienating them from - ie: if you need to pack everything in a steamer trunk to escape being herded into cattle cars, you can memorize a seed phrase and no one can stop you from taking your wealth with you.
And any polity who may no longer wish to use dollars as the international lingua franca of trade, as the global foreign exchange reserve currency, to reduce the degree to which their forex reserves prop up American empire.
Sadly, all of these use cases appear increasingly relevant as time goes on.
I’ve got an Argentinian friend who sends crypto to his mother because he pays less than 0.5 % in fees and exchange rates instead of close to 5% using the traditional way. From now on I’ll call him a corrupt criminal.
You're describing the people that use actual cash to launder and hide, well, cash, and that have done so for centuries, long before crypto had even been invented.
A few web searches on <big bank name> + "money laundering scandal" (e.g. "HSBC money laundering scandal") can offer valuable insights.
There is no doubt crypto processes trillions of dollars of illegal cash. Way easier for the illegal cash industry to wash their cash than ever before.